Hepatitis A Virus (HAV) – Picornaviruses

00:01 And then finishing up with Hepatitis A Virus.

00:04 This virus is resistant to acid which makes sense because it is typically a fecal oral transmission surviving passage through the gastric mucosa and the acid load, and then entering itself and causing eventual disease.

00:19 Transmission: fecal oral.

00:21 The picture you see is a transmission electron micrographic image of hepatitis A.

00:28 Again, clustered and looking very beautiful in clustered format.

00:33 So here's the pathogenesis for Hepatitis A Virus.

00:37 the primary replication occurs again in the point of entry, So, oropharynx passaging, through the stomach to intestinal epithelium.

00:46 Then the patients develop viremia after that first lytic phase, and the viruses then attack the hepatocytes.

00:55 At the initial point of contact binding and insertion of the virus into the hepatocytes, there's minimal damage.

01:03 Even as the viruses are passaging themselves again, creating new additional variants which are excreted into the bile through the common bile duct and into the stool for up to 10 days.

01:15 There is still a limited response, with the exception of a systemic immune or inflammatory response, which gives you the initial symptoms.

01:23 But as yet there's not a specific attack on the hepatocytes.

01:27 That comes later after the prodromal and preicteric symptoms.

01:31 Prodromal symptoms as the immune reaction is starting to develop and exposure to those variants.

01:37 It is low grade fever, malaise, anorexia, your common typical viral syndrome.

01:43 The preicteric symptoms.

01:45 So this is as the immune system is starting to rev up and starting to recognize that indeed, we have some damaged hepatocytes to address.

01:53 This starts to get much more gastrointestinal in its approach.

01:57 So, nausea, vomiting, the abdominal pain is crappy and nonspecific.

02:03 Many patients describe it as lower down instead of over the liver, which is somewhat interesting, but pain can be referred anywhere.

02:10 Patients also have fevers which increase in nature and they start to have rigors.

02:15 Generally feeling, again, like a miserable patient with the flu.

02:20 However, the flu is not followed in most cases by jaundice.

02:24 And when the patient then progresses to the enteric disease.

02:28 This is when they're now starting to get evidence of transient thankfully, but acute liver failure.

02:34 Inflammatory reaction targeting those infected and lytic hepatocytes, which is causing decreased past to the bile and a backup of bilirubin into the body.

02:46 So these patients have jaundice.

02:48 Their urine is excreting very dark evidence of bilirubin.

02:52 When one checks their liver numbers, their liver tests, the transaminases, the AST, ALT all of these are elevated.

03:01 That all goes with Hepatitis A Virus.

03:04 So diagnosis, both clinical but also as serologic assessment for Immunoglobulin M antibody to the hepatitis A virus, Why IgM? Because we actually now have vaccine product which can create an IgG protection and that is mostly protective.

03:23 It has a very good efficacy. But nothing else is not 100%.

03:28 So, serologic detection of Immunoglobulin M would suggest acute infection with hepatitis A.

03:35 And there are very few things to cause a false positive.

03:38 Treatment: Well, actually treatment is prevention as best we can because Hepatitis A is sewage or fecal associated.

03:46 So having proper treatment of the water supply through the municipal water supply, chlorine is effective in this.

03:53 Certainly good hygienic practices.

03:56 Again, washing hands wherever and whenever you go anyplace, avoidance of contaminated food and water.

04:02 Well, kind of hard to do if you don't know that they are contaminated, and because Hepatitis A is a fecal oral transfer, one could have exposure to a friend, a food server, a health care worker who is actively viremic and expressing Hepatitis A contagious variants into their stool and then could be exposed to their hands.

04:25 So for yourself, washing the hands is important.

04:29 Especially for travelers and those living in parts of the world that are endemic for Hepatitis A or exposure to that.

04:39 There is a very successful vaccine as I just mentioned, which is highly recommended.

04:44 In fact, in the States, it is part of a routine recommended or even required vaccine schedule for preschool-aged children because Hepatitis A is now becoming quite so common.

04:56 Treatment: Mostly for those who are immunocompromised, and unable to respond to the virus on their own is to give immunization with Hepatitis A specific immunoglobulin, or even polyclonal immunoglobulin.

05:09 However, most of the rest of us are able to make an appropriate immune response, and we just need enough time to get past the act of infection and to recover fully 100%.

05:21 So, this is a longer session is discussing some of the most important viruses in terms of especially pediatrics, with exposure to the enteroviruses as a whole.

05:31 Probably key to remember here is that the disease associated with each of these viruses has so much to do with the tropism, the target of the virus in terms of where it causes disease.

05:44 Viruses all caused disease in one way, by lysing their host cell and precipitating an immune reaction.

05:52 And when that immune reaction targets a disease selling the liver, or the brain, or the kidneys, or the throat, or the hands and the feet, all causes different manifestations.

06:01 Remember those and you'll be good.